Introduction: Metabolic dysfunction-associated steatohepatitis (MASH) is a is linked to type II-diabetes and marked by steatosis, steatohepatitis, fibrosis and eventually HCC. The number of patients with MASH-derived HCC is increasing worldwide. Currently, the first line of cancer treatment drugs are immune checkpoint inhibitors (ICIs). Although ICls have been approved by the FDA for various cancers, it has been reported that the response rate for HCC is low, and the development of new therapeutic drugs including ICIs for HCC is expected. Therefore, a mouse model for evaluating MASH-derived liver cancer is needed for drug discovery against HCC. In this study, in order to examine whether the STAM mouse, a MASH-HCC model mouse, can be used for the evaluation of ICIs, we conducted an analysis of immunohistochemistry and RNA-seq related to the immuno-oncology (IO) of HCC derived from STAM mice.
Methods: MASH was induced in male mice by a single subcutaneous injection of 200 µg streptozotocin solution 2 days after birth and feeding with high fat diet after 4 weeks of age. The mice were sacrificed and livers collected at 6, 8, 10, 12, 16, 20 and 24 weeks of age. For RNA-seq analysis, total RNA from the left lateral lobe was isolated using RNeasy mini kit. Liver specimens were stored at -80°C embedded in Optimal Cutting Temperature compound for immunohistochemistry (IHC). IHC for CD3, CD4, CD8, FOXP3, a-SMA and FAP was performed.
Results: Expression analysis of IO-related genes was performed. Increased expression was observed in CCl5, CD4, CD8a, CD274, CXCR4, CXCR10 and PDCD1. Additionally, mutations were observed in some genes. As a result of IHC, CD3, CD4, CD8, a-SMA and FAP-positive signals were detected in the peri-tumor region. Furthermore, CD8-positive signals were also detected in the intra-tumor region.
Conclusion: STAM mouse model, is the model that allows the evaluation of drugs that genetic mutations, immune cells, and tumor microenvironment in addition to molecular targeted drugs.
T. Hashiguchi: None.
